Dive computer with free dive mode and wireless data transmission

ABSTRACT

A dive computer with a free dive mode and/or wireless data transmission capabilities. In one embodiment the invention relates to a diving apparatus including a dive computer having a free dive mode, where the dive computer is configured to calculate a nitrogen loading in the free dive mode using a default value which is the fraction of oxygen in air, and where the free dive mode is used when a diver makes a dive without a self-contained underwater breathing apparatus. Another embodiment includes a method of operating a dive computer including recording two or more first identifiers, receiving pressure information from two or more pressure transmitters, the pressure information comprising second identifiers and pressure measurements, determining whether the pressure information contains one of the two or more first identifiers, and displaying a message indicative of the pressure information that contains one of the two or more first identifiers.

FIELD OF INVENTION

The present invention relates generally to underwater exploration andmore specifically to an apparatus and techniques for allowing free divesin conjunction with traditional underwater dives.

BACKGROUND OF THE INVENTION

The development of self-contained breathing systems has enabled humansto scuba dive and remain underwater for several hours. The ability toremain underwater for an extended period of time can enable divers toreach considerable depths and cover expansive distances in exploringunderwater terrain. Dive computers can provide useful measurements andmonitor critical factors for divers making such dives possible.

Divers often enjoy free diving. During a free dive, a diver does not usea self-contained breathing system but instead holds his/her breath. Whenconsiderable depths are reached during a free dive, the nitrogen loadingof a diver can be impacted. To assist a diver who executes a free divein conjunction with a traditional dive, dive computers generally includea feature that disables the dive computer for a period of time after afree dive. Disabling the dive computer is typically intended todiscourage the diver from diving until the diver's nitrogen loading hasreturned to normal.

SUMMARY OF THE INVENTION

The present invention relates to a dive computer having a free divemode. In one embodiment the invention relates to a diving apparatusincluding a dive computer having a free dive mode, where the divecomputer is configured to calculate a nitrogen loading in the free divemode using a default value which is the fraction of oxygen in air, andwhere the free dive mode is used when a diver makes a dive without aself-contained underwater breathing apparatus.

In another embodiment, the invention relates to a method of operating adive computer including accepting an input specifying one or more modesof operation, where the one or more modes of operation comprises a freedive mode, and calculating a nitrogen loading in the free dive modeusing the fraction of oxygen in air.

In yet another embodiment, the invention relates to a dive systemincluding a pressure transmitter including a first pressure transducerconnected to a processor unit, a transmitter connected to the processorunit, a memory connected to the processor unit, where the first pressuretransducer is configured to measure pressure information, and where thetransmitter is configured to transmit the pressure information to one ormore dive computers, the one or more dive computers including a receiverconfigured to receive the pressure information from two or more pressuretransmitters, a processor coupled to the receiver, and a display coupledto the processor, where the processor is configured to show pressureinformation on the display received from at least one of the two or morepressure transmitters.

In still yet another embodiment, the invention relates to a method ofoperating a dive computer including recording two or more firstidentifiers, where each first identifier is associated with a pressuretransmitter, receiving pressure information from two or more pressuretransmitters, the pressure information comprising second identifiers andpressure measurements, determining whether the pressure informationcontains one of the two or more first identifiers, and displaying thepressure information that contains one of the two or more firstidentifiers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a dive computer in accordance withan embodiment of the present invention;

FIG. 2 is a flow chart illustrating a method of operating a divecomputer in accordance with an embodiment of the present invention;

FIG. 3 is a flow chart illustrating a method of selecting a mode ofoperation for a dive computer in accordance with an embodiment of thepresent invention;

FIG. 4 is a flow chart illustrating a method of calculating nitrogenloading in accordance with an embodiment of the present invention;

FIG. 5 is a flow chart illustrating a method of determining whether thenitrogen loading exceeds acceptable thresholds in accordance with anembodiment of the present invention;

FIG. 6 is a flow chart illustrating a method of determining divecomputer functions in accordance with an embodiment of the presentinvention;

FIG. 7 is a schematic illustration of an embodiment of a dive computerand a wireless tank pressure transducer unit in accordance with anembodiment of the present invention;

FIG. 8 a is a schematic illustration of an embodiment of the wirelesspressure transducer of FIG. 7;

FIG. 8 b is a schematic illustration of an embodiment of the receiverunit of the dive computer depicted in FIG. 7;

FIG. 8 c is an illustration of a data packet that can be used with thedive computer and wireless pressure transducer of FIG. 7;

FIG. 9 is a side view of a communication system illustrating two diversusing wireless pressure transducers and dive computers in accordancewith embodiments of the present invention; and

FIG. 10 is a flow chart illustrating a method of operating a divecomputer that includes a wireless pressure transducer in accordance withan embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, dive computers in accordance withembodiments of the present invention are illustrated. The dive computerscan be placed in a plurality of modes, including a free dive mode, gaugemode and a normal dive mode. The normal mode can be used for generalunderwater scuba diving, while the gauge mode can be used by diversusing an advanced breathing gas. The free dive mode can be used when adiver wishes to execute a dive without assistance from an external airsupply and while holding his/her breath.

Dive computers in accordance with embodiments of the invention cancalculate and store nitrogen loading in many modes, including the freedive mode. Once nitrogen loading has been calculated, dive computers candetermine whether the calculated nitrogen loading is below default ordiver specified thresholds. In the free dive mode, the dive computerscan be operational following a free dive, enabling a diver to performother dives without waiting for a predetermined period of time. Thenitrogen loading calculated in the free dive mode can be carried over tothe other modes of operation. In this way, the physiological effects ofa free dive are accounted for in subsequent dives by the dive computer.Therefore, a diver can scuba dive after one or more free dives usingdive computers in accordance with embodiments of the invention.

Dive computers in accordance with embodiments of the invention can be apart of sophisticated communication systems. Dive computers can becapable of communication with external devices using a variety ofprotocols and over wired or wireless mediums. In one embodiment, a divecomputer can communicate with an external pressure transducer thatmonitors the pressure in the diver's tank and transmits informationwirelessly to the dive computer. In such case, the dive computer can beworn on the wrist of the diver. The wireless pressure transducer cancommunicate pressure information to more than one dive computer so thata first diver can monitor the pressure of a second diver's tank as wellas the pressure of his own dive tank. In some embodiments, the diver'smask can include a visual display and/or an audio device thatcommunicates wirelessly with a hand held or wrist mounted dive computer.

Turning now to FIG. 1, a dive computer in accordance with an embodimentof the present invention is illustrated. The dive computer 10 includes aprocessor 12 that is connected to memory 14, clock circuitry 18 and aninput/output interface 20. The input/output interface 20 is connected toa number of devices that can be used to communicate with a user or otherdevices. In the illustrated embodiment, these devices include a pressuretransducer 22, a keypad 24, a display 26, a communications port 28 and amicrophone 30.

A dive computer can include a number of functions which provideinformation to a diver. Dive computers can provide current depth, themaximum depth achieved during a dive, whether stop time will be requiredfor decompression and if so, the number of stops along with the durationof those stops, dive time elapsed, water temperature, ascent or descentrate, air time remaining, gas pressure and approximate position. Divecomputers often also provide warnings and user programmable thresholdsfor those warnings.

Although a particular embodiment of a dive computer is shown in FIG. 1,a free dive mode can be implemented and/or operated on any typical divecomputer. A typical dive computer can include the necessary componentsor sensors to measure the parameters of a decompression algorithm. Theparameters of a standard decompression algorithm are well known in theart and can include depth, pressure, and other parameters. Anotherparameter commonly included in a decompression algorithm is the gasmixture. The gas mixture typically includes oxygen, nitrogen, and somepercentage of other gases. Decompression algorithms generally assume astandard or default gas mixture for diver consumption unless the diverspecifies otherwise (i.e. a custom or user specified mixture).

Returning to FIG. 1, the processor 12 receives information from theclock circuitry 18, pressure transducer 22 and the input/outputinterface 20 and selectively stores the information in memory 14. In oneembodiment, the processor is implemented using a MSP430F148 manufacturedby Texas Instruments Incorporated of Dallas, Tex. However, the processorcould be implemented using discrete logic components or several separateprocessing elements that share information.

The memory 14 can be used to store data logged by the dive computer 10,to temporarily store information during the performance of calculationsand to store software used to control the operation of the processor 12.The memory 14 need not be a single integrated circuit and can beconstructed from a number of integrated circuits having distinctproperties. In the illustrated embodiment, the memory 14 includesnon-volatile memory circuits 34 to store software for controlling theprocessor 12, manufacturer settings, user settings, calibration data andnitrogen loading. In addition, the memory 14 also includes a removablememory device 36 that is used to store data logged during a dive such asimages, a dive profile, dive logs, nitrogen loading, audio recordings,and/or video games. The memory can also be connected to a digital camera(not shown) that is provided to enable the capture of images during adive and to enable the use of these images as part of a dive log ifdesired by the user. In one embodiment, the removable memory device 36is a flash memory card conforming to any number of standards such asMultiMediaCard or MMC standard.

The clock circuitry 18 can be used to measure the passage of time.Typically the clock circuitry 18 will incorporate a quartz crystal thatis used to generate a periodic signal that can be observed in order tomeasure the passage of time. The clock circuitry 18 can also besynchronized with an external clock to enable time to be expressed inabsolute terms using a time, a day, a month and a year. In oneembodiment the clock circuitry is part of the MSP430F149 microcontrollerdescribed above.

The input/output interface 20 can be constructed from any variety ofwires, antennas, transmitters, receivers, connectors and buffers. Theconfiguration of the input/output interface 20 is dependent on theinput/output devices that are connected to the dive computer. In theembodiment shown in FIG. 1, the input/output devices include a pressuretransducer, a keypad, a display, a communications port and a microphone.In other embodiments, any other combination of input/output devices canbe connected to the dive computer via the input/output interface. In oneembodiment, the portion of the input/output interface connected to thepressure transducer includes a standard analog to digital converter. Inanother embodiment, the processor includes an analog to digitalconverter. In addition, the input/output interface uses a display driversuch as an MSP430F4250 manufactured by Texas Instruments of Dallas, Tex.In some embodiments, analog content from the microphone 30 is convertedto digital content by an analog to digital converter.

The pressure transducer 22 can be used to measure the pressure of thewater in which the dive computer is immersed. In one embodiment a17887.A Low Pressure Transducer manufactured by Pelagic Pressure Systemsof San Leandro, California can be used to construct the pressuretransducer 22. In other embodiments, other components and/or circuitrycapable of generating an electrical signal indicative of the waterpressure in which the dive computer is immersed can be used.

A keypad 24 is typically provided to enable the user to enterinformation concerning the dive or to direct the processor 12 to providethe user with information. In one embodiment, the keypad 24 includes oneor more buttons, toggles, joysticks or equivalent devices with which theuser can provide instructions to the processor 12. In an exemplaryembodiment, the diver can use the keypad to select the mode ofoperation, a threshold, or a calculation to display.

A display 26 is typically provided to present information in a graphicalmanner to the user. Information that can be provided to the userincludes depth and/or time. If the dive computer 10 performs otherfunctions, information relating to these functions can also becommunicated using the display 26. In one embodiment, the display canprovide information relating to the air time remaining. The air timeremaining is the time that a diver can remain at the diver's currentdepth and still surface with the tank pressure reserve establishedduring the diver's configuration of the dive computer. Air timeremaining is calculated based on the diver's gas consumption and depth.In one embodiment, tank pressure can be measured once each second and anaverage rate of consumption is calculated over a ninety second period.This rate of consumption can then be used in conjunction with knowledgeof the depth dependence to predict the breathing gas required for a safeascent including any required compression stops.

In one embodiment, the display can provide information about the divetime remaining. The dive time remaining is the amount of time remainingbefore acceptable levels of nitrogen loading within the diver's body areexceeded, acceptable levels of oxygen accumulation are exceeded, or airtime remaining decreases below an amount required to ascend. In oneembodiment, the diver can specify a preferred nitrogen loading level.The time to fly is the amount of time that the diver should wait beforeriding in an airplane or driving to higher elevations. In oneembodiment, the display can provide information about the desaturationtime. The desaturation time can be defined as the theoretical timerequired for a diver's body to eliminate all residual nitrogen at sealevel, and is based on the amount of nitrogen loading accumulated duringa dive or set of repetitive dives.

Other input or output devices in addition to those described above canbe connected to a dive computer in accordance with the presentinvention. In one embodiment, speakers are connected to the input/outputinterface to enable the playback of recorded speech, to allow a diver tolisten to music during a dive or to provide an audible warning to thediver. In other embodiments, other combinations of devices can be usedto meet the information requirements and data recording requirements ofa diver during a dive.

As discussed previously, a dive computer can have several modes ofoperation. In one embodiment, a dive computer can have a normal mode, agauge mode, and a free dive mode. In other embodiments, a dive computercan have a free dive mode and one or more other dive modes. In severalembodiments, the dive computer performs a number of common functions, orfunctions that are performed during each dive mode.

A flow chart illustrating a method of operating a dive computer inaccordance with an embodiment of the present invention is shown in FIG.2. The method 50 includes the steps of selecting (100) a mode ofoperation, calculating (200) nitrogen loading, determining (300) whethernitrogen loading exceeds acceptable thresholds, and using (400) thecalculated nitrogen loading to determine dive computer functions. Divecomputer functions associated with nitrogen loading can include air timeremaining, dive time remaining, time to fly and desaturation time.

Dive computers can be placed in various modes by the diver depending onthe type of dive to be executed. A flow chart illustrating a method forselecting a mode of operation for a dive computer in accordance with anembodiment of the present invention is shown in FIG. 3. In the method100, the processor is placed (102) in a default mode in the illustratedexample. The diver can then select (104) a mode of operation by pressingone or more buttons on the keypad (not shown). Depending on the one ormore buttons pressed, the processor enters either a normal dive mode(106), a gauge dive mode (108), or a free dive mode (110). After thedive is performed, the diver can select (104) another mode of operation.

In other embodiments, the dive computer can have two or fewer modes, oneof which is a free dive mode or its functional equivalent. In someembodiments, the dive computer can have more than three modes, includinga free dive mode or its functional equivalent. In many embodiments, themodes can have different names but perform similar functions. In oneembodiment, the default mode can be a mode other than the normal divemode.

In many of the dive modes, the dive computer makes calculations ofnitrogen loading using a decompression algorithm. A number of techniquesare known for calculating nitrogen loading. A flow chart illustrating amethod of calculating nitrogen loading in accordance with an embodimentof the present invention is shown in FIG. 4. In the method 200, theprocessor measures (202) depth, time and other decompression algorithmparameters using one or more pressure transducers (not shown), the clockcircuitry (not shown), or other sensors (not shown).

The processor then determines (204) whether or not the diver has madeprior dives within a twenty four hour period. If the diver did make oneor more dives, the processor retrieves (206) the residual nitrogenloading calculated for each dive within a twenty four hour time periodand continues. Following nitrogen retrieval or if the diver did not makea prior dive, the processor then determines (208) whether or not thecurrent dive is a free dive. If the current dive is a free dive, thenthe processor calculates (210) the nitrogen loading with a decompressionalgorithm using a fixed default value that is the fraction of oxygen inair, and any prior (i.e. residual) nitrogen loading within the twentyfour hour period. In one embodiment, the fixed default value for thefraction of oxygen in air is set at twenty one percent. As previouslydiscussed, decompression algorithms generally assume a standard ordefault gas mixture for diver consumption unless the diver specifiesotherwise. In the free dive mode, the decompression algorithm uses afixed default value that is the fraction of oxygen in the air at sealevel. This is similar to according the diver the air he/she lastbreathed at the surface for a dive in the free dive mode. In severalembodiments, the value is set based upon the altitude at which the divecommences to reflect the gas mix at that altitude. If the current diveis not a free dive, the processor calculates (212) the nitrogen loadingusing a decompression algorithm and any prior (i.e. residual) nitrogenloading within the twenty four hour period. After calculating nitrogenloading, whether in the free dive mode or not, the processor stores(214) the nitrogen loading calculated for the dive.

In one embodiment, a decompression algorithm such as the Buhlmanndecompression algorithm can be used to calculate the nitrogen loadingfor a free dive. The Buhlmann decompression algorithm is discussed inU.S. Pat. No. 6,321,177 issued Nov. 20, 2001 to Ferrero et al. In otherembodiments, decompression algorithms such as the varying permeabilitymodel or the reduced gradient bubble model can be used. Manydecompression algorithms are based on the research of John Haldane andimprovements commissioned by the DSAT (Diving Science and Technology)and PADI (Professional Association of Diving Instructors) organizations.Embodiments of the present invention can utilize one or more of thesealgorithms or any other algorithm that can be used to calculate nitrogenloading during a scuba dive.

In determining the decompression algorithm parameters, the processor cantake into account other measurements. In one embodiment, the processormeasures the pressure of compressed gases consumed by the diver during adive. In several embodiments, the processor measures the rate of ascentor descent and/or the maximum depth. The decompression algorithm can bebased on empirical data developed by Dr. Michael Powell in conjunctionwith the DSAT and PADI organizations. In one embodiment, the time periodfor checking for previous dives or retrieving the nitrogen loading canbe more than or less than twenty four hours. In several embodiments, theprior nitrogen loading is calculated as a sum of all the nitrogenloading calculations for prior dives within a twenty four hour timeperiod. In many embodiments, the processor stores the results ofnitrogen loading calculations in the memory (not shown). In oneembodiment, a single nitrogen loading calculation is stored thatincorporates the nitrogen loading of all the previous dives in the giventime period.

As nitrogen loading is calculated, the dive computer can determinewhether the nitrogen loading might be cause for alarm. A flow chartillustrating a method of determining whether the nitrogen loadingexceeds acceptable thresholds for a free dive mode in accordance with anembodiment of the present invention is shown in FIG. 5.

In the method 300, the processor determines (302) an acceptable nitrogenloading threshold. The threshold can be a default value or a userspecified value. The processor next checks (304) to see if the nitrogenloading is greater than the threshold. If the nitrogen loading is notgreater than the threshold, then the process ends (310). If the nitrogenloading is greater than the threshold, then the processor activates(306) an alarm. After the alarm is activated and the dive computer hasdetermined that the diver has returned to the surface with a level ofnitrogen loading greater than the threshold, then the processor disables(308) the dive computer for a period of time. After the dive computer isdisabled, the process ends (310).

In one embodiment, the dive computer is disabled for a period of twentyfour hours. In other embodiments, the dive computer is disabled for aperiod greater than or less than twenty four hours which is determinedto be an acceptable interval. In one embodiment, the processor canactivate an alarm without entering a disabled mode. In severalembodiments, the alarm can be a visual alarm such as a light emittingdiode or LED, sequence of LEDs or other display. In many embodiments,the alarm can be an audio alarm or a combination of audio and visualwarnings.

In other embodiments, the dive computer can determine whether thenitrogen loading exceeds acceptable thresholds for the gauge or normaldive modes. In these embodiments, the dive computer can determineacceptable nitrogen loading thresholds, give the diver instructions forcompleting decompression stops, account for completed decompressionstops in nitrogen loading calculations, and decide whether to enter adisabled mode based upon the results of nitrogen loading calculationsincorporating the effects of completed decompression stops. Thefunctions performed in the gauge and normal dive computer modes thatrelate to determining whether nitrogen loading exceeds acceptablethresholds would be generally known to a skilled artisan.

After the nitrogen loading is calculated, the dive computer can usethese values to calculate other dive computer functions. A flow chartillustrating a method of determining dive computer functions inaccordance with an embodiment of the present invention is shown in FIG.6. In the method 400, the processor calculates (402) the air timeremaining. The processor calculates (404) the dive time remainingpossibly using the calculated nitrogen loading. The processor calculates(406) the desaturation time using the calculated nitrogen loading. Thedesaturation time can be defined as the theoretical time required for adiver's body to eliminate all residual nitrogen at sea level.

The processor then checks (408) to see whether any of the calculatedvalues are greater than their respective thresholds. The thresholds aredefault values unless the user has specified a particular value orpercentage of the default value to be used instead. If any of thecalculated values exceed their respective thresholds, then the processoractivates (410) one or more alarms corresponding to the respectivethreshold exceeded. In many embodiments, audio and/or visual alarms canbe activated as discussed previously. If none of the calculated valuesexceeds their respective thresholds or after activating the alarms, theprocessor returns to calculating the dive computer functions usingnitrogen loading. In many embodiments, the calculations performed in402, 404 and 406 may be performed in any order. In several embodiments,one or more of the calculations (i.e., dive time remaining) may not beperformed until the diver requests the calculation by pressing an inputkey on the dive computer.

Divers engaging in free diving often follow a free dive with a secondfree dive or a dive using a self-contained underwater breathingapparatus (scuba dive). This is commonly referred to as repetitivediving. The U.S. Navy tables, which are known to one skilled in the art,describe empirical guidelines for making repetitive dives. The divingtables require a diver to stop for at least ten minutes at the surface(surface interval time) before beginning a second dive. If the diverdoes not have a surface interval time of at least ten minutes, it is nottreated as a repetitive dive. It is instead treated as a single dive.Although the invention is not bound by theory, it is thought that thedive tables offer more favorable (i.e. longer) bottom times forrepetitive dives than for a single dive. This thought is supported bythe fact that the longer the diver spends at the surface, the morenitrogen he releases from his blood.

In accordance with one embodiment of the invention, dive computershaving a free dive mode can allow a diver who has completed a free diveto make a second dive that is treated by the dive computer as arepetitive dive after just one minute of surface interval time. In thiscase, the second dive, which can be either a free dive or a scuba dive,is treated by the dive computer as a repetitive dive for the purpose ofcalculating the maximum dive time possible without decompression stops,nitrogen loading, oxygen loading and/or other parameters relevant toperforming single or repetitive dives. In other embodiments, the divecomputers can allow a diver who has completed a free dive to make asecond dive that is treated by the dive computer as a repetitive diveafter two minutes or after five minutes. Although the invention is notbound by theory, it is thought that the deviation from the diving tableis possible since the diver is not breathing compressed gas during thefree dive. The diver instead breathes the air he acquired at thesurface.

A pressure transducer that can broadcast pressure related information tomore than one diver can greatly assist divers when two or more diversare diving together. A schematic illustration of an embodiment of a divecomputer and a wireless pressure transducer in accordance with anembodiment of the present invention is shown in FIG. 7. In oneembodiment, the wireless pressure transducer can be located on a tankused by the diver (i.e. tank pressure transducer unit). The divecomputer 10′ includes a processor 12′ that is connected to memory 14′,clock circuitry 18′ and an input/output interface 20′. The input/outputinterface 20′ is connected to a number of devices that can be used tocommunicate with a user or other devices. In the illustrated embodiment,these devices include an ambient pressure transducer 22′, a keypad 24′,a display 26′, a receiver unit 27′, a communications port 28′ and amicrophone 30′. In another embodiment, the receiver unit 27′ can beconnected directly to the processor 12′. The operation of these divecomputer components except for the receiver unit 27′ is describedpreviously in the discussion of FIG. 1. In the illustrated embodiment,the ambient pressure transducer 22′ can measure the depth of the diverand the tank pressure transducer unit 23′ can measure the pressure ofthe gas in the diver's tank.

In operation, the tank pressure transducer unit 23′ can communicate withthe receiver unit 27′ of the dive computer. The tank pressure transducerunit 23′ is capable of transmitting data via various protocols andmethods. In many embodiments, the tank pressure transducer unit cancommunicate with the dive computer via a wireless or wired communicationlink. In one embodiment, wireless communication can be achieved using acommunication system that complies with the Bluetooth, or IEEE 802.15.1,standard. In another embodiment, wireless communication can be achievedusing one or more piezoelectric devices. In one or more embodiments,communication can be achieved using magnetic fields and techniques suchas pulse width modulation. In other embodiments, the wirelesscommunication can be achieved using other protocols and methods.

A schematic illustration of an embodiment of the tank pressuretransducer unit of FIG. 7 is shown in FIG. 8 a. In this embodiment, thetank pressure transducer unit can act as a wireless pressure transducer.In other embodiments, the tank pressure transducer is connected to thedive computer using a wired connection. The wireless pressure transducer23′ includes a high pressure sensor 420, an analog to digital converter(A/D) 422, a processor 424, a memory 426, a battery 428, a digital toanalog converter (D/A) 430 and a transmitter 432. The processor 424 isconnected to the A/D 422, memory 426, battery 428 and D/A 430. The A/D422 is connected to the high pressure sensor 420. The D/A 430 isconnected to the transmitter 432.

In operation, the high pressure sensor measures the pressure of gas inthe diver's tank (not shown) and outputs the pressure information to theA/D. The A/D converts the analog pressure information received from thehigh pressure sensor into digital information and outputs it to theprocessor. The processor can store the digital pressure information inthe memory. The memory can also store information unique to the wirelesspressure transducer like a serial number. The processor can receiveinformation from the battery regarding the status of the battery and/orthe amount of time remaining before the battery is exhausted. Theprocessor can assemble packets of information 450 including the serialnumber 452, pressure data 454, and battery data 456 as shown in FIG. 8c. In other embodiments, different formats of packets can be used wherethe packets include information related to pressure and a serial number.

The processor can output the data packets to the D/A. The D/A caninclude a pulse generator capable of encoding data packets using pulsewidth modulation. The pulse width modulated packets can be sent to thetransmitter. In one embodiment, the transmitter can include a buffer ortemporary memory for storing packets. The transmitter can include a coilcapable of sending the pulse width modulated packets using a magneticfield.

In other embodiments, the wireless pressure transducer is capable ofcommunicating using other wireless protocols. In such embodiments, othercomponents and/or additional components are used to implement thewireless communication.

An embodiment of the receiver unit of the dive computer shown in FIG. 7is shown in FIG. 8 b. The receiver unit 27′ includes a receiver 440 andan analog to digital converter (A/D) 442. The receiver can includeamplifiers, filters and/or coils appropriate to receive a magnetic fieldas known to a skilled artisan. The receiver 440 is connected to the A/D422 which is connected to the I/O interface 20′ (not shown). In anotherembodiment, the A/D is connected directly to the processor 12′ (notshown).

In operation, the receiver receives the pulse width modulated packets inthe form of a magnetic field. The receiver can use a coil to receive themagnetic field and produce a corresponding analog signal. The receiveroutputs the analog signal to the A/D. The A/D can reconstruct digitalpackets from the pulse width modulated signal. The A/D can include amemory for storing the received information (i.e. packets). The A/D canoutput received packets in digital form to the I/O interface 20′. Inother embodiments, the A/D can output digital information directly tothe processor 12′ (see FIG. 7).

The processor 12′ can compare the serial number 452 of each digitalpacket 450 received to identification/serial numbers stored in memory.In one embodiment, the diver has entered the storedidentification/serial numbers into the memory of the dive computer. Inthe event that the stored serial number does not match the serial numbercontained in the received packet, the processor can discard the packet.

In one embodiment, collisions of signals or interference from signalssent by multiple wireless pressure transmitters is avoided byconfiguring each wireless pressure transmitter with a timing sequence.The timing sequence can specify a particular period of time for eachwireless pressure transmitter to transmit. In this way, transmitters aregenerally transmitting at different times so that collisions and/orinterference between transmitters is avoided.

In other embodiments, the receiver unit is capable of communicatingusing other wireless protocols. In such embodiments, other componentsand/or additional components are contemplated to implement the wirelesscommunication.

Wireless communication can be quite useful as divers often dive ingroups of two or more. A side view of a communication systemillustrating two divers using wireless pressure transducers and divecomputers in accordance with embodiments of the present invention isshown in FIG. 9. The system includes a first diver 502 and a seconddiver 508. Communication system components attached to the first diver502 include a first dive computer 506 and a first wireless pressuretransducer 504. Communication system components attached to the seconddiver 508 include a second dive computer 512 and a second wirelesspressure transducer 510.

The dive computers 506 and 512 can be wrist mountable. The wirelesspressure transducers 504 and 510 can be mounted to the regulator firststage located on the upper portion of the diver's tank. In anotherembodiment, the wireless pressure transducers (WPTs) can be mounted inproximity to the tank by any appropriate attachment means.

The communication system of FIG. 9 can operate in a number of ways. Aflow chart illustrating a method of operating a dive computer thatincludes a wireless pressure transducer in accordance with an embodimentof the present invention is shown in FIG. 10. In the method 900, thedive computer can determine (902) whether it has been configured forwireless communication with a wireless pressure transducer (WPT). In oneembodiment, the dive computer determines whether or not it has beenconfigured by checking its memory to see if the identification numbersof any WPTs have been stored.

In the event that the dive computer has not been configured, the divecomputer determines (906) whether or not the diver wants to configurethe dive computer for communication with a WPT, or “buddy mode.” If thediver indicates that he wants to configure the dive computer, then thedive computer responds by storing (910) the identification number of theWPT that the diver wishes to monitor. If the diver indicates that hedoes not want to configure the dive computer, then the dive computerreturns to determining (902) if the dive computer has been configured.After storing the identification or serial number, the dive computerdetermines (914) whether the user wants to enter additional WPTidentification numbers. If the user indicates a desire to enteradditional identification numbers, then the dive computer responds bystoring (910) the identification number of the WPT entered by the user.In the event that the user does not want to enter additionalidentification numbers, the dive computer returns to determining (902)if the dive computer has been configured.

In the event that the dive computer has been configured, the divecomputer determines (904) whether or not the user wants to check buddypressure, or the pressure of WPTs that are configured for beingmonitored. If the user does not want to check buddy pressure, then thedive computer returns to checking (902) to see if the dive computer hasbeen configured. If the user presses a key indicating that the diverwants to check buddy pressure, the dive computer searches (908) for allWPTs in the area surrounding the dive computer. In one embodiment, thedive computer can receive the transmissions of all the WPTs within aradius of five feet. In another embodiment, the dive computer canreceive the transmissions of all the WPTs within a radius of ten feet.In yet another embodiment, the dive computer can receive thetransmissions of all the WPTs within a radius greater than ten feet.After searching for WPTs, the dive computer can determine (912) whetherit received pressure data from any WPTs from which it was configured toreceive data. If the dive computer received pressure data, the divecomputer displays (916) the pressure data for all WPTs from which itreceived pressure data. In the event that the dive computer did notreceive pressure data, the dive computer displays a message indicatingthat the pressure or buddy pressure was not found. In one embodimentwhere the dive computer receives pressure data from at least one of theWPTs from which it was configured to receive data, the dive computerdisplays a message indicative of the pressure data for at least one ofthe WPTs from which the dive computer received pressure data. In suchcase, the message can include an icon, symbol or text message indicativeof the pressure data or a warning based on the pressure data. In oneembodiment, the dive computer can display the pressure data for at leastone of the WPTs from which the dive computer received pressure data.

The WPTs can operate by transmitting pressure information wirelessly. Inone embodiment, the transmitted information can include a uniqueidentification number such as a serial number and the pressure of thetank which is being monitored by the WPT. In another embodiment, onlypressure information is transmitted. In several embodiments, theinformation can be transmitted wirelessly using a system that conformsto the Bluetooth, or IEEE 802.15.1, standard. In another embodiment, theinformation can be transmitted wirelessly using one or morepiezoelectric devices. In one or more embodiments, communication can beachieved using magnetic fields and techniques such as pulse widthmodulation. In other embodiments, other wireless protocols orcommunication systems can be used. In one embodiment, the dive computercan detect one or more WPTs in the vicinity of the dive computer andconfigure itself by storing the identification numbers of the detectedWPTs. This can be useful for configuring “buddy mode” before a dive.

The wireless pressure transmitters can be used by a single diver or twodivers as in the embodiment shown in FIG. 9. In other embodiments, morethan two divers can configure their dive computers to monitor thepressure of one or more of the other divers on a particular dive. Thedive computers capable of monitoring the pressure of other divers tankscan be hand held devices, wrist mounted, or otherwise mounted to thediver's person.

Variations, modifications, and other implementations of what isdescribed herein will occur to those of ordinary skill in the artwithout departing from the spirit and the scope of the invention asclaimed. Although the invention has been described with respect tocertain embodiments, it should be recognized that the invention includesthe claims and their equivalents supported by this disclosure. In manyembodiments, a user can specify nominal values for thresholds or apercentage of default values for thresholds. In one embodiment, thepercentage may be set such that the thresholds are equivalent to theirdefault values if the diver were diving at 3,000 feet elevation. Inseveral embodiments, a user can specify more conservative thresholds. Inother embodiments, a user can specify more aggressive thresholds. Insome embodiments, a user cannot specify thresholds that are moreaggressive than the default values.

1. A diving apparatus comprising: a dive computer having a free divemode; wherein the dive computer is configured to calculate a nitrogenloading in the free dive mode using a default value which is thefraction of oxygen in air; and wherein the free dive mode is used when adiver makes a dive without a self-contained underwater breathingapparatus.
 2. The diving apparatus of claim 1, wherein the dive computeris configured to compare a threshold with the calculated nitrogenloading.
 3. The diving apparatus of claim 2, wherein the dive computeris configured to activate an alarm based on the comparison of thethreshold and the calculated nitrogen loading.
 4. The diving apparatusof claim 1, wherein the dive computer is configured to calculate thenitrogen loading in the free dive mode using the default value and aresidual nitrogen loading.
 5. The diving apparatus of claim 4, whereinthe residual nitrogen loading is a sum of nitrogen loading calculationsmade over a prior time period.
 6. The dive apparatus of claim 1, whereinthe dive computer comprises: a processor; a pressure transducerconnected to the processor; a display connected to the processor; andclock circuitry connected to the processor; wherein the processor isconfigured to determine time using the clock circuitry; wherein theprocessor is configured to determine depth of submersion using thepressure transducer; and wherein the processor is configured to providedepth and time information using the display.
 7. The diving apparatus ofclaim 1, wherein the dive computer is configured to calculate at leastone of air time remaining, dive time remaining and desaturation time,the calculation based on the nitrogen loading.
 8. The diving apparatusof claim 1, wherein the dive computer is configured to allow the diverto perform a second dive that is treated as a repetitive dive followinga dive without a self-contained underwater breathing apparatus afterthirty seconds.
 9. The diving apparatus of claim 1, wherein the divecomputer is configured to allow the diver to perform a second dive thatis treated as a repetitive dive following a dive without aself-contained underwater breathing apparatus after one minute.
 10. Thediving apparatus of claim 1, wherein the dive computer is configured toallow the diver to perform a second dive that is treated as a repetitivedive following a dive without a self-contained underwater breathingapparatus after two minutes.
 11. The diving apparatus of claim 1,wherein the dive computer is configured to allow the diver to perform asecond dive that is treated as a repetitive dive following a divewithout a self-contained underwater breathing apparatus after fiveminutes.
 12. The diving apparatus of claim 1: wherein the dive computerhas a normal dive mode; wherein the dive computer is configured tocalculate nitrogen loading in the normal dive mode accounting for use ofa self-contained breathing apparatus; and wherein the dive computer isconfigured to allow a dive in the free dive mode following a dive in thenormal dive mode.
 13. The diving apparatus of claim 1: wherein the divecomputer has a normal dive mode; wherein the dive computer is configuredto calculate nitrogen loading in the normal dive mode accounting for useof a self-contained breathing apparatus; and wherein the dive computeris configured to allow a dive in the normal dive mode following a divein the free dive mode.
 14. A method of operating a dive computercomprising: accepting an input specifying one or more modes ofoperation, wherein the one or more modes of operation comprises a freedive mode; and calculating a nitrogen loading in the free dive modeusing the fraction of oxygen in air.
 15. The method of claim 14, whereinthe nitrogen loading calculation is a function of a residual nitrogenloading.
 16. The method of claim 14, further comprising comparing thecalculated nitrogen loading to a threshold.
 17. The method of claim 16,further comprising activating an alarm based on the comparison of thecalculated nitrogen loading to the threshold.
 18. The method of claim14, further comprising using the calculated nitrogen loading tocalculate air time remaining, dive time remaining and/or desaturationtime.
 19. The method of claim 14, further comprising: determining a timeusing a clock circuitry; determining a depth of submersion using apressure transducer; and displaying the depth and time.
 20. The methodof claim 14, further comprising allowing a diver to perform a seconddive that is treated as a repetitive dive following a dive without aself-contained underwater breathing apparatus after thirty seconds. 21.The method of claim 14, further comprising allowing a diver to perform asecond dive that is treated as a repetitive dive following a divewithout a self-contained underwater breathing apparatus after oneminute.
 22. The method of claim 14, further comprising allowing a diverto perform a second dive that is treated as a repetitive dive followinga dive without a self-contained underwater breathing apparatus after twominutes.
 23. The method of claim 14, further comprising allowing a diverto perform a second dive that is treated as a repetitive dive followinga dive without a self-contained underwater breathing apparatus afterfive minutes.
 24. The method of claim 14, where the one or more modesfurther comprise a normal dive mode, the method further comprising:calculating a nitrogen loading in the normal dive mode, the calculationaccounting for use of a self-contained breathing apparatus; and allowinga dive in the free dive mode following a dive in the normal dive mode.25. The method of claim 14, where the one or more modes further comprisea normal dive mode, the method further comprising: calculating anitrogen loading in the normal dive mode, the calculation accounting foruse of a self-contained breathing apparatus; and allowing a dive in thenormal dive mode following a dive in the free dive mode.
 26. A divesystem comprising: a pressure transmitter comprising: a first pressuretransducer connected to a processor unit; a transmitter connected to theprocessor unit; a memory connected to the processor unit; wherein thefirst pressure transducer is configured to measure pressure information;and wherein the transmitter is configured to transmit the pressureinformation to one or more dive computers; the one or more divecomputers comprising: a receiver configured to receive the pressureinformation from two or more pressure transmitters; a processor coupledto the receiver; and a display coupled to the processor; wherein theprocessor is configured to show pressure information on the displayreceived from at least one of the two or more pressure transmitters. 27.The dive system of claim 26, wherein the memory of each of the two ormore pressure transmitters is configured to store identificationinformation associated with the transmitter.
 28. The dive system ofclaim 27, wherein the transmitter of each of the two or more pressuretransmitters is configured to transmit the identification information.29. The dive system of claim 26, wherein the transmitter of each of thetwo or more pressure transmitters is configured to transmit a wirelesssignal.
 30. The dive system of claim 26, wherein the receiver of the oneor more dive computers is configured to receive a wireless signal. 31.The dive system of claim 30, wherein the wireless signal comprises amagnetic field.
 32. The dive system of claim 31, wherein the magneticfield is pulse width modulated.
 33. The dive system of claim 26, whereinthe first pressure transducers are configured to measure a tankpressure.
 34. The one or more dive computers of claim 26, furthercomprising a second pressure transducer, wherein the second pressuretransducer is configured to measure an ambient water pressure.
 35. Amethod of operating a dive computer comprising: recording two or morefirst identifiers, where each first identifier is associated with apressure transmitter; receiving pressure information from two or morepressure transmitters, the pressure information comprising secondidentifiers and pressure measurements; determining whether the pressureinformation contains one of the two or more first identifiers; anddisplaying a message indicative of the pressure information thatcontains one of the two or more first identifiers.
 36. The method ofclaim 35, further comprising converting the pressure information into adigital packet.
 37. The method of claim 35, wherein determining whetherthe pressure information contains one of the two or more firstidentifiers further comprises comparing a first identifier with a secondidentifier.
 38. The method of claim 35, further comprising: determininga time using clock circuitry; determining a depth of submersion using apressure transducer; and displaying the depth and time.
 39. The methodof claim 35, wherein the message indicative of the pressure informationcomprises at least one of a symbol, icon and text message.
 40. Themethod of claim 35, wherein the message indicative of the pressureinformation is the pressure information.